Two-step process for production of RON-enhanced mixed butanols and diisobutenes

ABSTRACT

A two-step process for the oligomerization and hydration of a mixed butenes feed is provided and is implemented in a two-stage system. The two-step process yields a product consisting of diisobutenes (DIBs) and mixed butanols. The DIBs are produced via the selective oligomerization of isobutene in a first stage and the mixed butanols are produced via the hydration, in a second stage, of mixed butenes that remain unreacted in the first stage.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a divisional of U.S. Non-Provisional patentapplication Ser. No. 14/103,439, filed Dec. 11, 2013, the entirecontents of which is incorporated by reference herein as if expresslyset forth in its respective entirety herein.

TECHNICAL FIELD

The present invention relates to a process for the production of mixedalcohols along with butene oligomers. More specifically, the presentinvention relates to a two-step process for oligomerizing and hydratinga feed stream that includes butene isomers to produce butene oligomersand mixed butanols, which can be used as blending components withreduced RVP and increased RON and octane sensitivity.

BACKGROUND

While hydrocarbon fuels remain as the dominant energy resource forinternal combustion engines, alcohols, especially methanol and ethanol,have also been used as fuels. Currently, the primary alcohol fuel isethanol, which is commonly blended into gasoline in quantities of 5 to10%. In fact, various fuels being produced today consist primarily ofalcohols. For example, E-85 fuel contains 85% ethanol and 15% gasoline,and M-85 fuel has 85% methanol and 15% gasoline. While ethanol possessesexcellent octane enhancement properties, there are several drawbacks toits use as a gasoline component, including: energy deficiencies (ethanolprovides approximately 39% less energy than gasoline), high blendingReid Vapor Pressure (RVP) (at 10% of blending, the RVP=11 psi), andincompatibility with existing transportation facilities.

Historically, lead (Pb) was added to gasoline to increase its octanerating and thereby improve its antiknock properties. However, the use oflead in gasoline has now been eliminated in most countries for healthand environmental reasons. In response to the need to increase octaneratings in the absence of lead, methyl-tertiary-butyl-ether (MTBE) wascommercially introduced as an octane enhancing component of gasoline inthe United States and other countries in the late 1970s. Legalrestrictions on the minimum oxygen content of some gasolines—introducedin the 1990s as a means of reducing environmentally harmful exhaustemissions—encouraged a further increase in the concentration of MTBE ingasoline, which, by then, was being blended at up to 15% by volume.While MTBE is still widely used in the United Kingdom, its use has beenin gradual decline in other regions of the world due to concerns aboutthe harmful effects of MTBE itself. Specifically, its existence ingroundwater has led to a decline in its use in countries such as theUnited States, where some states have actively legislated against itsuse. Today, in order to meet performance and legal requirements, thefuel industry in the United States is now replacing MTBE with fermentedgrain ethanol. However, producing the necessary quantities of grainethanol to replace MTBE is problematic in specific regions, and the useof ethanol as a gasoline component has other drawbacks as discussedabove.

Certain other alcohols (i.e., butanols), as well as butene oligomers(e.g., diisobutenes (DIBs)) can be used as combustible neat fuels,oxygenate fuel additives, or constituents in various types of fuels. TheBTU content of butanols and diisobutenes is closer to the energy contentof gasoline than either methanol or ethanol. Butanols have been thoughtof as second generation fuel components after ethanols. Specifically,2-butanol and tert-butanol can be particularly advantageous fuelcomponents, as they have blending octane sensitivities and energydensities comparable to those of MTBE and have been shown to have lowerRVP at 15% concentrations relative to comparable ethanol blends.Similarly, DIB is a non-oxygenated fuel component with many advantagesover other fuel additives. For instance, DIBs have higher RON, betteranti-knock quality, and higher energy content compared with MTBE, aswell as a lower RVP than MTBE, butanols and ethanol.

Butanols can be produced via the hydration of butenes, a process thattypically utilizes an acid catalyst. While the production of butanolsvia hydration of butenes is a commercially important process, it istypically very costly. DIBs are produced via theoligomerization/dimerization of butenes, in particular isobutene. Thedimerization of isobutene is also generally performed using acidcatalysts, such as sulfuric acid and hydrogen fluoride; however, thesecatalysts tend to be highly corrosive in nature.

Both butanols and DIBs provide certain advantages over other existingfuel components. However, until now, there have not been any processesin place that are particularly effective for converting mixed olefinsinto alcohols—especially butenes into butanols—while also dimerizingpart of the mixed olefins feed into oligomers such as DIBs withoutrequiring the costly separation of either mixed butenes isomers in thefeed or the mixed butanol isomers in the product. The combination ofbutanols and DIBs as a fuel additive would lead to enhanced RON, octanesensitivity, and energy density, as well as decreased RVP in gasoline.

Thus, there is a need for alternative gasoline oxygenates that possesscomparable RON enhancement properties and a higher energy content thanMTBE and ethanol, but that also eliminates the environmental andcompatibility concerns of MTBE and ethanol. Additionally, there is aneed for alternative fuel additives that lower the RVP of fuel in theabsence of MTBE. Finally, there is a need for an alternative processthat allows for both the hydration and oligomerization of mixed butenesto alcohols and oligomers, namely butanols and DIB, which can be used asoctane enhancing components.

SUMMARY

The present invention is directed to a process for producingRON-enhanced mixed butanols, potential replacement oxygenates for MTBEand ethanol as fuel additives. More specifically, this invention relatesto a two-step process (two-stage system) for producing DIBs and mixedbutanols from the oligomerization and hydration of a mixed butene feedcontaining a mixture of the four butene isomers: 1-butene, 2-cis-butene,2-trans-butene and isobutene. The DIBs are produced via the selectiveoligomerization of isobutene (in the absence of water) in a firstreactor containing an oligomerization catalyst, while the other buteneisomers remain primarily unreacted. In one embodiment, at least amajority of and preferably, at least a substantial portion of theisobutene is oligomerized (dimerized) to form DIBs. The mixed butanolsare produced via the hydration of the butene feed in a subsequent secondreactor containing a hydration catalyst. In a preferred embodiment, then-butenes (1 and 2-butenes) hydrate to form 2-butanol and any remainingisobutene hydrates to form tert-butanol.

In one embodiment, the temperature maintained in the both reactors is80-250° C. and the pressure maintained in the reactors is approximately10-80 bar.

In another embodiment, the temperature maintained in the olimerizationreactor is 30-100° C. and the pressure maintained in the reactors isapproximately 5-80 bar while the temperature maintained in the hydrationreactor is 100−250° C. and the pressure maintained in the reactors isapproximately 10-80 bar.

This invention provides a distinct advantage over other oligomerizationand hydration processes, as it allows for enhanced control over thequantities of DIB and tert-butanol produced. Because DIB has a lowerRPV, higher RON, octane sensitivity, and energy content compared withtert-butanol, a product with greater DIB content relative totert-butanol is preferred for gasoline blending purposes. Thus, theability to increase the production of DIB via oligomerization whiledecreasing the yield of tert-butanol via hydration results in aRON-enhanced mixed butanol final product that possesses superiorgasoline blending properties.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

A more complete understanding of the invention and its many features andadvantages will be attained by reference to the following detaileddescription and the accompanying drawing. It is important to note thatthe drawing illustrates only one embodiment of the present invention andtherefore should not be considered to limit its scope.

FIG. 1 shows a diagram of a two-step process in accordance with anembodiment of the invention; and

FIG. 2 is a graph showing the effect of various exemplary blendcomponents on RON.

DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS

As mentioned hereinbefore, the prior art contains a number of processesfor the oligomerization of mixed butenes and processes for the hydrationof olefins into alcohols; however, until now, there have not been anyprocesses in place that are particularly effective for converting amixed butene feed into butanols, while also oligomerizing part of themixed butene feed into oligomers such as DIBs.

The present invention overcomes the deficiencies and limitations of theprior art and is directed to a two-step process for the oligomerizationand hydration of mixed butenes to produce a mixed butanols and DIBproduct, which can being used as superior gasoline blending components.As described herein, the two-step process of the present inventionallows for improved control over the composition (amount percentage) ofthe DIBs in the final product, thereby allowing the composition of thefinal product stream to be tailored.

Mixed Olefins (Butenes)

Mixed butenes have four structural isomers: 1-butene, 2-cis-butene,2-trans-butene, and isobutene. Optionally, other low olefins, such aspropylene and ethylene, can also be present in the feed as describedbelow.

Diisobutenes (DIBs) or Isooctenes

Diisobutenes include two isomers of 2,4,4-tri-methyl-1-pentene and2,4,4-trimethyl-2-pentene.

Mixed Butanols

Mixed butanols include at least two of the following compounds:1-butanol, 2-butanol, tert-butanol, and isobutanol. Preferredembodiments of the present invention include only 2-butanol andtert-butanol as described below.

Oligomerization (Dimerization)

Oligomerizations of mixed butenes as described herein includeoligomerizations of all butene isomers, preferably oligomerizations ofisobutene and more preferably, the dimerization of isobutene. Theoligomerization fraction can be extremely rich in dimers (isooctenes orDIBs), and can be added as such to the gasoline cuts to give a very highquality gasoline.

Major compounds that can be derived from the oligomerization of mixedbutenes include but are not limited to: diisobutenes (DIBs),tri-isobutenes, dimer of isobutene and n-butenes, and trimer ofisobutene and n-butenes can all be derived from the oligomerization ofmixed butenes. It will be appreciated by one of skill in the art thatother products can be formed. As is known, DIB is a non-oxygenative fuelcomponent with many advantages as a blending agent, such as higher RON,higher octane sensitivity or better anti-knock quality, higher energycontent compared to MTBE and alkylates, and/or lower RVP than MTBE andethanol.

Dimerization of Isobutene

Hydration of Mixed Butenes

Hydration of butenes to butanols are commercially important reactions asthe products find several important industrial applications. Generally,the hydration of mixed butenes is selected to only produce 2-butanol andtert-butanol; however, the formation of other compounds is possible.Mixed butanols, primarily 2-butanol and tert-butanol, can be used asoxygenative-type premium gasoline additives.

-   -   Isobutene+water□tert-butanol□□    -   n-butene+water□2-butanol

Other possible products that can be derived from the hydration of mixedbutenes include but are not limited to etherification products ofbutanols and butenes or butanols itself. Butanols generally have goodgasoline octane blending characteristics and can be used in combinationas petroleum additives with other oxygenates, such as ethanol and MTBE.

The Present Oligomerization/Hydration Process

As described herein, processes for production of mixed butanols andbutene oligomers from a mixed butene feed are provided as embodiments ofthe present invention. Additionally, processes for producing fuelcompositions that include oligomers and alcohols prepared from buteneare also provided as embodiments of the present invention.

In one embodiment of the present invention, a method (process) forproducing alcohols and oligomers from olefins is provided. Morespecifically, the process is a two-step process in which mixed olefinsare oligomerized in the absence of water in the first step and hydrationof the remaining mixed olefins takes place in the second step withadequate unit operations to separate the products as needed anddescribed herein. A product stream that includes oligomers and alcoholsis formed. In certain embodiments, the mixed olefins are in the form ofa feedstock that is a mixed butene feedstock and the product streamincludes DIBs and mixed butanols. In one embodiment, the product streamthat includes DIBs and mixed butanols can be combined with a fuelcomponent to produce a fuel composition. The fuel component of the fuelcomposition can be selected from gasoline, diesel, jet fuel, aviationgasoline, heating oil, bunker oil, or combinations thereof. In certainembodiments, the resultant fuel composition will have increased RON andreduced RVP, without the presence of other chemicals that can havedeleterious effects on the environment.

The source of the mixed olefin (butene) stream can vary and canencompass any number of different sources of feedstocks (streams) thatare suitable for use in the present invention. In some embodiments ofthe present invention, the mixed olefin stream can be discharge streamfrom an FCC unit or thermal cracking unit, raffinates from an MTBEprocess, a raffinates stream from TBA process, a liquefied petroleum gas(LPG) stream, or combination thereof. In one embodiment, the mixedolefin (butene) feed comes from a refinery gas stream.

Various types of olefins can be included in the mixed olefin stream. Asmentioned herein, in certain embodiments, mixed olefin stream caninclude a mixed butene stream. In another embodiment, the mixed olefinstream can include propylene, n-butene, 2-butene, isobutylene, pentenes,hexenes, olefins having more than 6 carbons with at least two butenes,or combinations thereof. Other olefins that can be used in accordancewith other embodiments include ethylene, propene, butenes, pentenes, orother higher olefins. It will be understood that other suitable sourcesfor the mixed olefin stream and types of olefins can used so long asthey are suitable for the intended application described herein andachieve a product stream having the desired characteristics that are setforth herein. In yet another embodiment, the mixed butene feed used inthe present invention typically contains the four butene isomers invarying quantities as set forth below.

Most commercialized butene hydration processes are designed either withpure feeds, like 1-butene and isobutene, or mixed feeds for theselective isobutene hydration. The process conditions are typicallyselected to maximize the yield of either 2-butanol or the yield oft-butanol. Because both 2-butanol and t-butanol are valuable oxygenatesand octane enhancers for fuels, certain embodiments of the presentinvention use a two-stage (two-step) based system and process that iseffective for the production of highly desired butanols, such as2-butanol and t-butanol, and butene oligomers for gasoline componentsfrom cheap mixed butenes.

With respect to the oligomerization of olefins, different butene isomershave different activities toward dimerization or oligomerization. Forexample, it is typically difficult for 2-butenes to form thecorrespondent dimers or oligomers. In contrast, isobutene is predisposedto being dimerized or oligomerized.

In accordance with one embodiment of the present invention, the presenttwo-stage process is such that isobutene is selectively oligomerized(dimerized) to DIB during the oligomerization reaction and the otherbutenes remain primarily unreactive due to the catalyst selection and/oroperating (reaction) conditions. During the hydration phase of theprocess, all four isomers of butene can be effectively hydrated to formmixed butanols. The resultant product stream thus includes DIBs andmixed butanols.

As described herein, the catalyst systems of the present invention areconfigured to perform the intended functions in the two differentstages, namely, the oligomerization stage and the hydration stage, ofthe present system/process. Accordingly, the present invention entailsthe use of an oligomerization catalyst and a hydration catalyst. It willbe appreciated that the amount of each catalyst can vary depending uponthe mixed olefin stream being sent to the process. It will beappreciated that any number of suitable catalysts can be used for theoligomerization catalyst and the hydration catalyst so long as therespective catalyst operates in the manner described herein and achievesthe intended objectives. In one embodiment, the oligomerization catalystand/or the hydration catalyst comprise an acidic catalyst, such as ionicexchange resins (catalysts). Alternatively, the oligomerization catalystand/or the hydration catalyst comprise substituted/non-substitutedheteropoly acids. For example, a heteropoly acid (cesium substituted)can be prepared according to a process described in Miao Sun, et al.,“Significant Effect on Acidity on Catalytic Behaviors of Cs-SubstitutedPolyoxometalates for Oxidative Dehydrogenation of Propone,” AppliedCatalysis A: General (2008); pp. 212-221, which is hereby incorporatedby reference in its entirety. Commonly owned U.S. patent applicationSer. No. 14/091,137, which is hereby incorporated by reference in itsentirety, sets forth catalysts that can be used as catalysts for use inthe present invention.

The oligomerization catalyst and hydration catalyst can be the same orthey can be different catalysts.

FIG. 1 illustrates one exemplary for performing the oligomerization andhydration of mixed olefins (butenes) in a two-stage process inaccordance with the present invention. FIG. 1 likewise shows anexemplary flow scheme. The system 100 can thus be thought of asincluding two different stages, namely, a first stage, identified at101, in which the oligomerization of the olefins (butenes) occurs and asecond stage, identified at 201, in which the hydration of the olefins(butenes) occurs. As described herein, each stage has associatedequipment and an associated catalyst to produce the intended products.

The first stage 101 includes a first reactor 110 in the form of anoligomerization reactor and the second stage 201 includes a hydrationreactor 200.

The reactants are delivered to the oligomerization reactor 110 and thehydration reactor 200 in the following manner. A source of feedstock(e.g., a mixed olefin feed and more particularly, a mixed butenes feed)is identified at 120 and is fluidly connected (e.g., by means of a fluidconduit 121 (such as a pipe)) to the oligomerization reactor 110. Beforeentering an inlet of the oligomerization reactor 110, the feedstockpasses through a first compressor 130 and a first heat exchanger 132that are disposed along the conduit 121 between the source of feedstock120 and the oligomerization reactor 110. The heat exchanger 132 islocated downstream of the compressor 130.

The compressor 130 and the heat exchanger 132 are configured to adjustthe pressure and temperature, respectively, of the feedstock prior to itentering the oligomerization reactor 110 and thus also control theoligomerization reactor pressure and temperature. In one exemplaryembodiment, the oligomerization reactor conditions are: a pressurebetween about 10 bar and about 70 bar and a temperature between about30° C. and about 160° C. In other words, the first compressor 130 servesto compress the mixed butene feed stream to between about 10 bar andabout 70 bar and the first heat exchanger 132 serves to adjust thetemperature of this mixture to between about 100° C. and about 160° C.

The oligomerization reactor 110 is configured to perform oligomerizationof the feedstock introduced therein and under oligomerizationconditions. The oligomerization reactor 110 can be in the form of asingle stage reactor having an inlet connected to the conduit 121 toreceive the feedstock 120. Within the reactor 110, an oligomerizationcatalyst 125 is contained. For example, the oligomerization catalyst 125can be located in one or more zones or regions of the reactor 110.

As described below in greater detail, the oligomerization catalyst 125is of a type which oligomerizes a mixed olefin feedstock underoligomerization conditions. More specifically, the oligomerizationcatalyst 125 is of a type and is selected so as to cause theoligomerization of isobutene (in the olefin feedstock) to DIBs, whilethe remaining mixed butenes remain inert (i.e., unreacted). In otherwords, the oligomerization catalyst 125 is selected so as to selectivelyoligomerize the isobutene in the feedstock but does not oligomerize theother isomers of butene, thereby leaving these other isomers unreacted(i.e., the unreacted n-butenes and any unreacted isobutene). As aresult, the first stage can maximize DIBs production and thus, the finalproduct stream can include optimal DIBs content.

The remaining unreacted mixed butenes and DIB form a first productstream that exits the oligomerization reactor 110 via a conduit 135 andis introduced to a low pressure separator 140. In the low pressureseparator 140, the DIB component of the first product stream is removedvia conduit 141 for collection, while the unreacted butene stream exitsvia a different conduit 143. In other words, the low pressure separator140 is configured and is operated under conditions to separate DIB fromthe other constituents of the first product stream (i.e., separation ofan oligomerized component from an unreacted component).

Upon exiting the low pressure separator 140 via conduit 143, theunreacted mixed butene stream is then contacted with a fresh waterstream 145 at a location along the conduit 143. The fresh water stream145 mixes with the unreacted mixed butene stream to produce a mixturethat flows within the conduit 143 to a second compressor 146 and secondheat exchanger 148 that are disposed along the conduit 143, with thesecond heat exchanger 148 being disposed downstream of the secondcompressor 146. After flowing through both the second compressor 146 andthe second heat exchanger 148, the mixture flows to the hydrationreactor 200. The second compressor 146 and the second heat exchanger 148are again configured to adjust the pressure and temperature,respectively, of the feedstock prior to it entering the hydrationreactor 200 and thus also control the hydration reactor pressure andtemperature. In one exemplary embodiment, the hydration reactor 200conditions are: a pressure between about 10 bar and about 70 bar and atemperature between about 100° C. and about 160° C. In other words, thesecond compressor 146 serves to compress the liquid mixture to betweenabout 10 bar and about 70 bar and the second heat exchanger 148 servesto adjust the temperature of this mixture to between about 100° C. andabout 160° C.

The hydration reactor 200 is loaded with a hydration catalyst 203 (suchthat the catalyst is located in one or more zones). As described belowin greater detail, the hydration catalyst 203 is of a type whichhydrates the mixture of fresh water and unreacted mixed butene streamunder hydration conditions. More specifically, the hydration catalyst203 is of a type and is selected so as to cause the n-butenes (unreactedbutenes in the mixture) to be hydrated into 2-Butanol and any remainingisobutene that is contained in the unreacted butene feed is hydratedinto tert-Butanol. In other words, the hydration catalyst 203 isselected so as to be of a type that hydrates the butenes in thefeedstock in the presence of water which is part of the mixtureintroduced into the hydration reactor 200. A mixed butanols productstream is produced as a result of the contact between the water andmixed butene mixture and the hydration catalyst.

The mixed butanols product stream then exits the hydration reactor 200via conduit 205, through which the mixed butanols product stream travelsto a high pressure separator 210. In the high pressure separator 210,the organic phase and the aqueous phase of the mixed butanols productstream are separated. The aqueous phase exits the high pressureseparator 210 via conduit 211 and the organic phase exits via conduit213. The aqueous phase represents a constituent of the stream that isnot desired in the final olefin based product stream.

The aqueous phase, through conduit 211, travels to an azeotropicdistillation column 220. In the azeotropic distillation column 220, thebutanol-water azeotrope is distilled out of the aqueous mixture andrecycled back into the high-pressure separator 210 via conduit 215. Asis known, an azeotrope is a mixture of two or more liquids in such a waythat its components cannot be altered by simple distillation. Thishappens because, when the azeotrope is boiled, the vapor has the sameproportions of constituents as the unboiled mixture. There are a numberof different techniques that can be used to separate the constituents ofthe azeotrope. One technique is azeotropic distillation in which anadditional agent, called an entrainer, that will affect the volatilityof one of the azeotrope constituents more than another. The azeotropicdistillation column 220 uses this type of technique to separate theconstituents (butanol and water). In the present arrangement, theremaining water in the azeotropic distillation column 220 exits viaconduit 217 where it is then recycled back to the hydration reactor 200.

The organic phase of the mixed butanols product stream—made up ofunreacted mixed butenes and mixed butanols—exits the high pressureseparator 210 via conduit 213 and travels to a debutenizer 240. As isknown, the debutenizer 240 is a type of fractional distillation columnused to separate butenes from other components during the refiningprocess. Distillation is the process of heating a liquid to vapor andcondensing the vapors back to liquid in order to separate or purify theliquid. Fractional distillation, as occurs in a debutenizer, is theseparation of a fraction—a set of compounds that have a boiling pointwithin a given range—from the rest of the mixture.

In the debutenizer 240, the unreacted mixed butenes are separated fromthe mixed butanols. The unreacted mixed butenes exit the debutenizer viaconduit 218 and are recycled back into the oligomerization reactor 110.The mixed butanols exit the debutenizer 240 via conduit 219, throughwhich they travel to connect with the DIB product discharged throughconduit 141 to form the final product identified at 300. It will beappreciated that this final product 300 which can be considered to be aproduct stream of RON enhanced mixed butanols can then undergoadditional processing and/or transportation to another site, such as astorage site.

As a result of the two-stage (two-step) process design and the operatingconditions in each of the reactors, along with the catalyst compositionsin the reactors, the DIBs content in the mixed butanols product 300 canbe altered (customized) in order to meet the blending requirements ofthe fuel. This ability to alter the DIBs content is not possible asimultaneous oligomerization/hydration process, such as that describedin applicant's own previous U.S. patent application publication No.2013/0104449 (the '449 publication). In such simultaneous process, themixed butenes feed stream is combined with water before being introducedinto a common reactor which operates under oligomerization and hydrationconditions to convert the mixed olefins into alcohols (e.g., butenesinto butanols) and simultaneously dimerize the mixed olefins intooligomers, such as DIBs. Since two different processes, namelyoligomerization and hydration, occur in the same reactor, the mixedolefins, and in particular, isobutene, are both oligomerized andhydrated resulting in a mixed butanols and DIB product stream. Since DIBproduction is also in the context of a competing and simultaneoushydration process, the content of DIBs is not optimized and cannot beindependently controlled to yield a desired product stream with optimalamount of DIBs. In contrast, the present invention achieves theseobjectives.

More specifically and according to one embodiment, as a result ofoligomerization catalyst and reaction conditions, at least a majority ofand preferably, at least a substantial portion of the isobutene presentin the mixed butene feed is oligomerized in the first reactor. Theconversion percentage of isobutene is between 30-100%. The mixedbutanols product formed in the second stage is later combined with theDIB from the first stage to create the final product, which can be usedas a superior gasoline constituent.

Thus, one will appreciate that one advantage of the present invention isthe ability to produce DIBs and mixed butanols in a common scheme thatimplements a single two-step process with each stage (step) beingindependent from the other. Alcohols (e.g., butanols) and DIBs can bothbe prepared from the isobutene in the initial mixed butenes feed stream,but there have not been any butene hydration processes in place thatefficiently convert mixed butenes into butanols while, at the same time,dimerizing part of the butene feed into oligomers, such as DIBs. Asmentioned above, the '449 publication addresses this same issue bysimultaneously hydrating and oligomerizing mixed butenes to producealcohols and DIBs. However, the advantage of the present invention overthe '449 publication is that the present invention provides bettercontrol over the composition of DIBs in the final product since thefirst stage maximizes DIBs formation and the DIBs is later combined withthe alcohols (butanols) from stage two. Specifically, by increasing theDIB content of the final product, the concentration of tert-butanol,which has poorer blending properties compared with 2-butanol and DIB s,is reduced.

Another advantage is that the products of the present invention can beused as superior gasoline constituents without separation. The mixedbutanols serve as oxygenated octane enhancers to provide for increasedcombustion efficiency, thereby reducing emissions. The DIBs complementthe mixed butanols by serving as high energy content octane enhancersand low RVP gasoline components.

The advantageous qualities of DIBs and butanols as gasoline componentscompared with other known gasoline components are further explained bythe data in Table 1 and FIG. 2. This data stems from an experiment inwhich the five compounds listed below (MTBE, ethanol, 2-butanol,tert-butanol, and DIB) are each blended into a base gasoline inconcentrations of 5, 10, 15, 20, and 25%, respectively, and theirrespective characteristics are determined. In particular, Table 1 setsforth the trends in RON, Mon, octane sensitivity, and RVP, respectively.

TABLE 1 Blending Properties Comparison for Common Fuel Blends EnergyDensity RVP or Higher 15% Blending Blending Blending Heating Value v/vBlends RON MON Sensitivity (MJ/Kg) Blend Base 85.8 81.0 4.8 45.6 9.46gasoline MTBE 124.7 103.5 21.2 38.0 9.6 Ethanol 139.8 106.6 33.2 29.911.5 2-Butanol 116.6 97.8 18.8 37.3 10.4 tert-butanol 108.6 89.3 19.337.3 9.96 DIB 132.1 99.2 32.9 48.2 8.5

As shown by Table 1 and FIG. 2, compared with other common fuelconstituents, DIB has the lowest RVP, the highest energy density, thesecond highest blending RON, and the second highest blending octanesensitivity (essentially equivalent to that of ethanol). Additionally,2-butanol and tert-butanol have blending octane sensitivities and energydensities comparable to MTBE, and result in a lower RVP at 15%concentrations than ethanol. Based on this data, it can be inferred thatincreasing the DIB content of the mixed butanols product stream improvesits blend properties by enhancing RON, octane sensitivity, and energydensity while decreasing the RVP. Thus, the combination of DIBs andbutanols creates a high-octane fuel additive with the potential toreplace ethanol as a superior oxygenate and the present invention allowsfor optimization of DIBs content due to the two-step process schemedescribed herein.

As mentioned, the alcohols and oligomers in the product stream made inaccordance with the embodiment of the present invention can be used as acomponent in fuel compositions or as a neat fuel composition. Forexample, in one embodiment, a neat fuel composition can be preparedaccording to the methods described herein that include a mixed butanolfuel having an octane rating suitable for use in combustion orcompression engines. In another embodiment, a fuel composition thatincludes a fuel component and a mixed butanol fuel is provided. In anembodiment, the fuel component can include gasoline, diesel, jet fuel,aviation gasoline, heating oil, bunker oil, or combination thereof. Inan aspect, the mixed butanols can include n-butanol, 2-(+/−)-butanol,iso-butanol, tert-butanol, or combination thereof; or alternatively,2-(+/−)-butanol and tert-butanol. In certain embodiments, the mixedbutanols can include at least two butanol compounds selected fromn-butanol, 2-(+/−)-butanol, iso-butanol, tert-butanol, or combinationthereof; or alternatively, 2-(+/−)-butanol and tert-butanol.

The mixed alcohols (butanols) stream made in accordance with the variousembodiments of the present invention can be used in other types of fuelcompositions, as will be apparent to those skilled in the art and are tobe considered within the scope of the present invention.

As described herein, the process and system of the present invention canbe thought of as being, according to one embodiment, a selectiveoligomerization of isobutene in the presence of the other butene isomersand in the absence of water and the hydration of all four butene isomerstogether in the presence of water (i.e., 1-butene, trans-2-butene,isobutene and cis-2-butene) with the oligomerization and hydrationreactions implemented in two separate reactors.

The process and the system of the present invention provide a number ofadvantages over the conventional oligomerization and hydrationprocesses. These advantages include but are not limited to: (1)providing an alternative gasoline oxygenate that possesses comparableRON enhancement properties and higher energy content than MTBE andethanol, while eliminating the associated compatibility andcontamination issues; (2) utilizing the products of the presentinvention—namely, DIBs and mixed butanols—as superior gasolineconstituents without separation; and (3) providing better control overthe composition of DIBs in the mixed butanols final product thanprevious methods for simultaneously oligomerizing and hydrating mixedolefin feeds.

EXAMPLES

The following examples are provided to better illustrate embodiments ofthe present invention, but they should not be construed as limiting thescope of the present invention.

The following experiments were conducted at a pilot plant having theconfiguration and characteristics of the system shown in FIG. 1. Thereaction conditions for Examples 1 and 2 are listed in the below Table2.

Example 1

The catalyst used for both the oligomerization stage and the hydrationstage was an ion-exchange resin and more particularly, the catalyst wasan ion-exchange resin that is commercially available under the tradename 0008-3 from Kairui Chemicals Co. Ltd of China. This exemplary resinis a macroporous strong acid cation exchange resin which is made up ofopaque beads and is a sulfonic acid cation exchanger in hydrogen form. Atotal of 30 mL of catalyst was loaded. The mixed butenes were purchasedfrom a local gas company and used without any purification. Thecomposition of the butene mixture (the mixed butenes) is 1-butene 21%,isobutene 35%, 2-cis-butene 19% and 2-trans-butene 25%. The unreactedbutenes were analyzed by an online gas chromatography which could be fedinto the second stage of hydration reactor.

Example 2

The catalyst used for both the oligomerization stage and the hydrationstage was a heteropoly acid catalyst and more particularly, the catalystwas a Cs salt of a heteropoly acid which is synthezed according to theprocess described in U.S. Ser. No. 14/092,601 and described in Miao Sun,Jizhe Zhang, Chuanjing Cao, Qinghong Zhang, Ye Wang, Huilin Wan. AppliedCatalysis A: General 349 (2008) 212-221).

TABLE 2 Tail gas composition for the Total hydration reactor butenesProducts selectivity (%) 2- conversion C8 C12 C16 C20 trans- 1- iso-2-cis- (%) olefins olefins olefins olefins butene butene butene buteneExample 1: Catalyst Kairui 008-3 Reaction Conditions: Temperature: 40°C.; pressure: 20 bar; LHSV: 0.63 hr−1; test period: 780 min 42.8 88.29.3 2.6 0 37.78 31.5 2.77 27.95 Example 2: catalyst Cs-HPA ReactionConditions: Temperature: 40° C.; pressure: 20 bar; LHSV: 0.63 hr−1; testperiod: 405 min 43.7 65.1 29.8 4.5 0.5 38.26 30.2 3.08 28.46

The results of Examples 1 and 2 demonstrate that isobutene can beselectively converted into DIBs. The butenes composition after theoligomerization reactor is significantly changed. The iso-butene contentis reduced over 90% in the feed stream.

Example 3

The catalyst for Example 3 is the same catalyst used in Example 1.Example 3 demonstrates that at a higher dimerization temperature, all ofthe isomers of butenes can be oligomerized. However, isobutene is moreprone to be converted into oligomers. Results and conditions are shownin the below Table 3.

TABLE 3 Example 3: Catalyst Kairui 008-3 Reaction Conditions: 160° C.;pressure: 20 bar; LHSV: 0.33 hr−1; test period: 1020 min Tail gascomposition for the hydration reactor Total butenes Products selectivity(%) 2- conversion C8 C12 C16 C20 trans- 1- iso- 2-cis- (%) olefinsolefins olefins olefins butene butene butene butene 78 58.5 31.9 8.2 1.459.36 10 0.91 29.73

While the present invention has been described above using specificembodiments, there are many variations and modifications that will beapparent to those having ordinary skill in the art. As such, thedescribed embodiments are to be considered in all respects asillustrative, and not restrictive. Therefore, the scope of the inventionis indicated by the appended claims, rather than by the foregoingdescription. All changes that come within the meaning and range ofequivalency of the claims are to be embraced within their scope.

What is claimed is:
 1. A method for preparing a gasoline composition,the method comprising the steps of: providing a fuel grade gasoline;providing an octane enhancing composition comprising an oligomerized andhydrated hydrocarbon product stream formed by a process that includesthe steps of: introducing a hydrocarbon feed that comprises mixedbutenes including isobutene and n-butenes into a first reactor vesselunder reaction conditions that are operable to oligomerize isobuteneinto diisobutenes; contacting the hydrocarbon feed with anoligomerization catalyst within the first reactor vessel, theoligomerization catalyst being of a type that selectively oligomerizesthe isobutene into diisobutenes; separating the diisobutenes fromunreacted butenes to form a diisobutene stream; introducing theunreacted butenes into a second reactor vessel in the presence of waterand under reaction conditions that operable to hydrate the unreactedbutenes including the unreacted n-butenes and any unreacted isobutene;contacting the unreacted butenes with a hydration catalyst within thesecond reactor vessel to hydrate the unreacted butenes to form a mixedbutanols stream; and combining the diisobutene stream and mixed butanolsstream to form the product stream; and combining the fuel grade gasolineand octane enhancing composition to form the gasoline composition. 2.The method of claim 1, wherein the octane enhancing composition iscombined with the fuel-grade gasoline after preparation without furtherpurification.
 3. The method of claim 2, wherein the octane enhancingcomposition is present in an amount of between about 5 and 30% by weightof the gasoline composition.
 4. The method of claim 1, wherein then-butenes comprise 1-butene, 2-trans-butene, and 2-cis-butene.
 5. Themethod of claim 1, wherein the hydrocarbon feed is introduced into thefirst reactor vessel in the absence of water.
 6. The method of claim 1,wherein prior to introducing the hydrocarbon feed into the first reactorvessel, the hydrocarbon feed passes through: (a) a first compressorwhich compresses the hydrocarbon feed to a first predetermined pressure;and (b) a first heat exchanger that adjusts a temperature of thehydrocarbon feed to a first predetermined temperature.
 7. The method ofclaim 6, wherein the first predetermined pressure is between about 5 barand 100 bar and the first predetermined temperature is between about 30°C. and about 250° C.
 8. The method of claim 1, wherein the step ofcontacting the unreacted butenes with a hydration catalyst within thesecond reactor vessel results in the n-butenes being hydrated to2-butanol and any isobutene being hydrated to tert-butanol.
 9. Themethod of claim 1, further including the steps of: (a) passing the mixedbutanols stream from the second reaction vessel through a high pressureseparator which is configured to separate an organic phase containingunreacted mixed butenes along with extracted mixed butanols from anaqueous phase that is saturated with mixed butanols; (b) passing theseparated organic phase through a debutenizer column in which theorganic phase is separated and unreacted mixed butenes are removed; and(c) passing the separated aqueous phase to an azeotropic distillationcolumn in which alcohol-water azeotrope is distilled out of the aqueousphase.
 10. The method of claim 9, wherein the unreacted mixed butenesremoved from the debutenizer are recycled and combined with thehydrocarbon feed upstream of the first reactor vessel and thealcohol-water azeotrope is recycled back to the high pressure separatorfor further recover alcohols while water is recycled back to a locationupstream of the second reactor vessel.
 11. The method of claim 1,wherein the oligomerization conditions can be varied independent fromthe hydration conditions to maximize diisobutene formation in the firstreactor vessel from 5 mol % to a maximum of up to 100 mol % of isobutenein the hydrocarbon feed.
 12. The method of claim 1, wherein a conversionrate of converting isobutene to diisobutene in the first reactor vesselis between about 5 mol % and about 100 mol %.
 13. The method of claim 1,wherein the hydrocarbon feed consists essentially of butenes.
 14. Themethod of claim 1, further comprising the step of combining the productstream with a gasoline stream to produce a gasoline product havingincreased research octane number (RON) and reduced Reid vapor pressure(RVP) as compared to a second gasoline product having an absence of theproduct stream.
 15. The method of claim 1, wherein each of theoligomerization catalyst and the hydration catalyst comprises at leastone of an acidic catalyst and substituted/non-substituted heteropolyacids.
 16. The method of claim 15, wherein the acidic catalyst comprisesan ionic exchange resin.
 17. The method of claim 1, wherein theoligomerization catalyst and hydration catalyst are the same.
 18. Themethod of claim 1, wherein the conversion rate of converting isobuteneto diisobutene in the first reactor vessel is greater than 90%.
 19. Amethod for preparing a gasoline composition, the method comprising thesteps of: providing a fuel grade gasoline; providing an octane enhancingcomposition comprising an oligomerized and hydrated hydrocarbon productstream formed by a process that includes the steps of: introducing ahydrocarbon feed that comprises mixed butenes including isobutene andn-butenes into a first reactor vessel under reaction conditions that areoperable to oligomerize the butenes; contacting the hydrocarbon feedwith an oligomerization catalyst within the first reactor vessel, theoligomerization catalyst being of a type that selectively oligomerizesisobutene into diisobutenes; separating the diisobutenes from unreactedbutenes to form a diisobutene stream, wherein the step of separating thediisobutenes from the unreacted butenes comprises the step of:introducing the diisobutenes and the unreacted butenes from the firstreactor vessel into a low pressure separator that is configured toseparate the diisobutenes from the unreacted butenes including unreactedn-butenes and any unreacted isobutene; introducing the unreacted butenesinto a second reactor vessel in the presence of water and under reactionconditions that operable to hydrate the unreacted butenes including theunreacted n-butenes and any unreacted isobutene; contacting theunreacted butenes with a hydration catalyst within the second reactorvessel to hydrate the unreacted butenes to form a mixed butanols stream;and combining the diisobutene stream and mixed butanols stream to form aproduct stream; and combining the fuel grade gasoline and octaneenhancing composition to form the gasoline composition.
 20. The methodof claim 19, wherein prior to introducing the unreacted butenes into thesecond reactor vessel, water is added to the unreacted butenes,including the unreacted n-butenes, to form an aqueous mixture thatpasses through: (a) a compressor which compresses the aqueous mixture toa predetermined pressure; and (b) a heat exchanger that adjusts atemperature of the aqueous mixture to a predetermined temperature. 21.The method of claim 20, wherein the predetermined pressure is betweenabout 10 bar and 100 bar and the predetermined temperature is betweenabout 80° C. and about 250° C.